Digital upconversion for multi-band multi-order power amplifiers

ABSTRACT

The present disclosure relates to digital up-conversion for a multi-band Multi-Order Power Amplifier (MOPA) that enables precise and accurate control of gain, phase, and delay of multi-band split signals input to the multi-band MOPA. In general, a multi-band MOPA is configured to amplify a multi-band signal that is split across a number, N, of inputs of the multi-band MOPA as a number, N, of multi-band split signals, where N is an order of the multi-band MOPA and is greater than or equal to 2. A digital upconversion system for the multi-band MOPA is configured to independently control a gain, phase, and delay for each of a number, M, of frequency bands of the multi-band signal for each of at least N-1, and preferably all, of the multi-band split signals.

RELATED APPLICATIONS

This application is a continuation of U.S. Application Ser. No.13/558,455, filed Jul. 26, 2012, the disclosure of which is incorporatedherein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure is related to digital upconversion for multi-bandmulti-order power amplifiers.

BACKGROUND

A Multi-Order Power Amplifier (MOPA) is a power amplifier havingmultiple inputs where an input signal to be amplified by the MOPA issplit across the multiple inputs such that the resulting split inputsignals drive multiple amplification blocks. The split input signals aretypically created by analog circuitry or an intelligent digitalsplitting algorithm. The multiple amplification blocks operate togetherto produce, at an output of the MOPA, an amplified version of the inputsignal. Some examples of a MOPA include a 2-way Doherty amplifier, a3-way Doherty amplifier, a Linear Amplification with NonlinearComponents (LINC) amplifier, an Envelope Elimination and Restoration(EER) amplifier, and a Chireix amplifier.

MOPA operation requires that the split input signals be staticallyoffset in phase, gain, and delay with respect to one another. There areseveral analog approaches to achieving this control. One approach isRadio Frequency (RF) analog splitting of the input signal as part of aninput matching network of the MOPA (e.g., analog Doherty). Anotherapproach is baseband signal splitting followed by analog upconversion,where individual compensation of each upconverter is required to matchthe gain, phase, and delay in the upconversion path and additionalcorrection circuits and/or algorithms are required to correct for theamplitude and phase imbalance created by analog quadrature modulators.

Splitting the input signal in the analog domain is perhaps the simplestmethod, but the resulting split is frequency dependent and very limitedin capability. Although phase, gain, and delay match acrossamplification paths can be achieved by physical symmetry of thesplitting structure, compensating for any component variations becomesvery difficult. This type of split limits the efficiency that can beachieved by a MOPA that has multiple simultaneous inputs and requiresindependent signal control over a range of frequencies.

Baseband signal splitting has advantages over RF analog splitting butrequires that the upconversion chains be matched across the multipleinstances for the multiple split input signals so that the split made atbaseband remains intact after upconversion. Since upconversion istypically in the analog domain, this is a relatively difficult task forsecond order MOPAs but is extremely difficult for higher order MOPAs.Further, compensating gain, phase, and delay is frequency dependent and,even worse, is physical realization dependent (e.g., every unit builtneeds to be calibrated differently or an average calibration is used forall units which limits achievable performance).

One issue with existing approaches to offsetting the gain, phase, anddelay of the split input signals provided to a MOPA is accuracy andcomplexity. As the order (i.e., the number of inputs) of the MOPAincreases, the complexity of existing solutions becomes nearlyinsurmountable. Another issue with existing approaches is that they arefrequency dependent. As such, they are not suitable for multi-band inputsignals.

SUMMARY

The present disclosure relates to digital up-conversion for a multi-bandMulti-Order Power Amplifier (MOPA) that enables precise and accuratecontrol of gain, phase, and delay of multi-band split signals input tothe multi-band MOPA. In general, a multi-band MOPA is configured toamplify a multi-band signal that is split across a number, N, of inputsof the multi-band MOPA as a number, N, of multi-band split signals,where N is an order of the multi-band MOPA and is greater than or equalto 2. A digital upconversion system for the multi-band MOPA isconfigured to independently control a gain, phase, and delay for each ofa number, M, of frequency bands of the multi-band signal for each of atleast N-1, and preferably all, of the multi-band split signals.Preferably, the gain, phase, and delay for each of the frequency bandsfor each of the multi-band split signals are independently controlledsuch that one or more performance parameters of the multi-band MOPA(e.g., linearity, efficiency, and/or output power) are optimized.

In one embodiment, for each of the M frequency bands of the multi-bandsignal, the digital upconversion system includes a digital signalsplitter that splits a digital baseband input signal for the frequencyband into N baseband split signals for the frequency band. Each of the Nbaseband split signals for the frequency band corresponds to a differentorder of the N orders of the multi-band MOPA. Further, for each of the Nbaseband split signals for each of the M frequency bands, the digitalupconversion system includes a digital upconverter that digitallyupconverts the baseband split signal to a desired upconversion frequencyto thereby provide a corresponding upconverted split signal. The digitalupconverter includes one or more calibration actuators that areconfigured to control a gain, phase, and delay of the upconverted splitsignal. After digital upconversion, there is a different upconvertedsplit signal for each of the orders of the multi-band MOPA for each ofthe frequency bands.

Further, in one embodiment, the digital upconversion system includes,for each of the N orders of the multi-band MOPA, a digital combiner anda digital-to-analog converter. The digital combiner is configured todigitally combine the upconverted split signals for the M frequencybands for the order of the multi-band MOPA to provide a combinedupconverted digital signal for the order of the multi-band MOPA. Thedigital-to-analog converter then converts the combined upconverteddigital signal into a combined upconverted analog signal for the orderof the multi-band MOPA. The combined upconverted analog signal is thenprocessed by analog circuitry to provide a corresponding multi-bandsplit signal to a corresponding input of the multi-band MOPA. The one ormore calibration actuators of the digital upconverters for the differentorders of the multi-band MOPA for each of the frequency bands of themulti-band signal are independently configured to independently controla gain, phase, and delay of each of the upconverted split signals. Inthis manner, the digital upconversion system independently controls thegain, phase, and delay for each frequency band for each of themulti-band split signals input into the multi-band MOPA. In oneembodiment, the gain, phase, and delay of each of the upconverted splitsignals is independently controlled to optimize one or more performanceparameters of the multi-band MOPA (e.g., linearity, efficiency, and/oroutput power).

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates a multi-band Multi-Order Power Amplifier (MOPA) thatamplifies a multi-band signal that is split across multiple inputs ofthe multi-band MOPA as multiple multi-band split signals, wherein again, phase, and delay for each frequency band of the multi-band signalfor each of the multi-band split signals is independently controlled inorder to optimize one or more performance parameters of the multi-bandMOPA according to one embodiment of the present disclosure;

FIG. 2 illustrates a system including a multi-band MOPA and a digitalupconversion system that independently controls a gain, phase, and delayfor each frequency band of the multi-band signal for each multi-bandsplit signal input to the multi-band MOPA such that one or moreperformance parameters of the multi-band MOPA are optimized according toone embodiment of the present disclosure; and

FIG. 3 illustrates one of the digital up-converters of FIG. 2 in moredetail according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

The present disclosure relates to digital up-conversion for a multi-bandMulti-Order Power Amplifier (MOPA) that enables precise and accuratecontrol of gain, phase, and delay of multi-band split signals input tothe multi-band MOPA. In this regard, FIG. 1 illustrates a multi-bandMOPA 10 having independent gain, phase, and delay calibration for eachfrequency band to be amplified by the multi-band MOPA 10 for each inputof the multi-band MOPA 10 according to one embodiment of the presentdisclosure. In general, the multi-band MOPA 10 operates to amplify amulti-band signal (S_(MB)) that is split across a number (N) of inputs12-1 through 12-N of the multi-band MOPA 10 as multi-band split signals(S_(MB-1) through S_(MB-N)). The number N is the number of inputs 12-1through 12-N of the multi-band MOPA 10 and is also referred to as an“order” of the multi-band MOPA 10. The number N is greater than or equalto 2. The multi-band signal (S_(MB)) has a number (M) of frequencybands, where M is greater than or equal to 2. The multi-band MOPA 10 maybe, for example, a multi-band Doherty power amplifier (e.g., a 2-way or3-way Doherty amplifier), a Linear Amplification with NonlinearComponents (LINC) amplifier, an Envelope Elimination and Restoration(EER) amplifier, and a Chireix amplifier.

As used herein, a “multi-band signal” is a signal that containsfrequency components occupying multiple frequency bands (i.e., a firstcontinuous frequency band, a second continuous frequency band, etc.)with no frequency components between adjacent frequency bands. Withineach frequency band, the multi-band signal includes what is referred toherein as a “narrowband signal” at a corresponding carrier frequency ofthe multi-band signal. As used herein, a “narrowband signal” is notnecessarily “narrowband” in the traditional sense, but has a bandwidththat is less than (i.e., narrower than) a total bandwidth of themulti-band signal. Notably, the narrowband signals in the frequencybands of the multi-band signal are preferably single band signals.However, in one alternative embodiment, one or more of the narrowbandsignals in one or more of the frequency bands of the multi-band signalmay itself be a multi-band signal.

As illustrated, the multi-band split signals (S_(MB-1) through S_(MB-N))provided to the inputs 12-1 through 12-N of the multi-band MOPA 10 aregenerated from a number (N) of split signals for each of the M frequencybands of the multi-band signal (S_(MB)), which are referred to as splitsignals S₁₋₁ through S_(1-N), . . . , S_(M-1) through S_(M-N),respectively. More specifically, as illustrated, the split signals S₁₋₁through S_(1-N) are for a first carrier frequency (f₁) for themulti-band signal (S_(MB)) (i.e., for a first frequency band of themulti-band signal (S_(MB))). Likewise, the split signals S_(M-1) throughS_(M-N) are for an M-th carrier frequency (f_(M)) for the multi-bandsignal (S_(MB)) (i.e., for an M-th frequency band of the multi-bandsignal (S_(MB))). A combiner 14-1 combines the split signals S₁₋₁through S_(M-1) (i.e., the split signals for the first order, or input,of the multi-band MOPA 10 for all M frequency bands) to provide themulti-band split signal (S_(MB-1)) for the input 12-1 of the multi-bandMOPA 10. Likewise, a combiner 14-N combines the split signals S_(1-N)through S_(M-N) (i.e., the split signals for the N-th order, or input,of the multi-band MOPA 10 for all M frequency bands) to provide themulti-band split signal (S_(MB-N)) for the input 12-N of the multi-bandMOPA 10. While not illustrated, the combiners 14-1 through 14-N arepreferably digital combiners, and digital-to-analog converters andanalog circuitry subsequent to the digital combiners further process theoutput of the digital combiners to provide the multi-band split signals(S_(MB-1) through S_(MB-N)). However, in FIG. 1, these elements areomitted for clarity and ease of discussion.

The multi-band split signals (S_(MB-1) through S_(MB-N)) are amplifiedby the multi-band MOPA 10 to provide a multi-band output signal(S_(OUT)). As discussed below in detail, a gain, phase, and delay ofeach of the split signals (S₁₋₁ through S_(1-N), . . . , S_(M-1) throughS_(M-N)) are independently controlled, or configured. As such, the gain(G₁₋₁), phase (φ₁₋₁), and delay (τ₁₋₁) of the split signal (S₁₋₁) arecontrolled independently from the gains, phases, and delays of all ofthe other split signals for all M of the frequency bands, the gain(G₁₋₂), phase (φ₁₋₂), and delay (τ₁₋₂) of the split signal (S₁₋₂) arecontrolled independently from the gain, phase, and delay of all of theother split signals for all M of the frequency bands, etc. In thismanner, a gain, phase, and delay for each of the M frequency bands foreach of the multi-band split signals (S_(MB-1) through S_(MB-N)) areindependently controlled. Preferably, the gain, phase, and delay of eachof the split signals (S₁₋₁ through S_(1-N), . . . , S_(M-1) throughS_(M-N)), and thus the gain, phase, and delay for each of the Mfrequency bands for each of the multi-band split signals (S_(MB-1)through S_(MB-N)), are independently controlled such that one or moreperformance parameters (e.g., efficiency, linearity, and/or outputpower) of the multi-band MOPA 10 are optimized. In one embodiment, theone or more performance parameters include efficiency and one or both oflinearity and output power. In one particular embodiment, the gain,phase, and delay of each of the split signals (S₁₋₁ through S_(1-N), . .. , S_(M-1) through S_(M-N)) are independently controlled to maximizeefficiency while maintaining sufficient linearity to satisfy one or morepredefined requirements for the multi-band MOPA 10 (e.g., predefinedemissions requirements).

Before proceeding, it should be noted that values for the gain, phase,and delay of each of the split signals (S₁₋₁ through S_(1-N), . . . ,S_(M-1) through S_(M-N)) may be selected, or calibrated, using anysuitable technique. In one particular embodiment, values for the gain,phase, and delay of each of the split signals (S₁₋₁ through S_(1-N), . .. , S_(M-1) through S_(M-N)) are selected in a factory calibrationprocess. For instance, one or more performance parameters of themulti-band MOPA 10 may be measured while adjusting the values for thegain, phase, and delay of each of the split signals (S₁₋₁ throughS_(1-N), . . . , S_(M-1) through S_(M-N)) using any suitable algorithmuntil the values that provide the desired optimization of the one ormore performance parameters are determined. These values may then bestored and utilized during operation of the multi-band MOPA 10. Inanother embodiment, the values for the gain, phase, and delay of each ofthe split signals (S₁₋₁ through S_(1-N), . . . , S_(M-1) throughS_(M-N)) may be selected dynamically based on measurements of themulti-band output signal (S_(OUT)) during operation of the multi-bandMOPA 10. In this manner, the values for the gain, phase, and delay ofeach of the split signals (S₁₋₁ through S_(1-N), . . . , S_(M-1) throughS_(M-N)) can be updated over time as needed to optimize the one or moreperformance parameters of the multi-band MOPA 10.

FIG. 2 illustrates a system 16 that includes a multi-band MOPA 18 and adigital upconversion system 20 for the multi-band MOPA 18 according toone embodiment of the present disclosure. In general, the multi-bandMOPA 18 operates to amplify a multi-band signal (S_(MB)) that is splitacross a number (N) of inputs 22-1 through 22-N of the multi-band MOPA18 as multi-band split signals (S_(MB-1) through S_(MB-N)). The number Nis the number of inputs 22-1 through 22-N of the multi-band MOPA 18 andis also referred to as an “order” of the multi-band MOPA 18. The numberN is greater than or equal to 2. The multi-band signal (S_(MB)) has anumber (M) of frequency bands, where M is greater than or equal to 2.The multi-band MOPA 18 may be, for example, a multi-band Doherty poweramplifier, (e.g., a 2-way or 3-way Doherty amplifier), a LINC amplifier,an EER amplifier, and a Chireix amplifier.

The digital upconversion system 20 digitally upconverts digital basebandsignals (S_(BB,1) through S_(BB,M)) for the M frequency bands of themulti-band signal (S_(MB)) and generates N multi-band analog signals(S_(ANALOG-1) through S_(ANALOG-N)) that, after further processing byanalog circuitries 24-1 through 24-N, provide the multi-band splitsignals (S_(MB-1) through S_(MB-N)) to the respective inputs 22-1through 22-N of the multi-band MOPA 18. More specifically, the digitalupconversion system 20 includes digital signal splitters 26-1 through26-M, digital upconverters 28(1-1) through 28(M-N) each including one ormore calibration actuators, digital combiners 30-1 through 30-N, anddigital-to-analog (D/A) converters 32-1 through 32-N connected as shown.The digital signal splitter 26-1 operates to split the digital basebandsignal (S_(BB,1)) into N baseband split signals (S_(BB,1-1) throughS_(BB,1-N)) each corresponding to a different order, or input, of themulti-band MOPA 18. The manner in which the digital signal splitter 26-1splits the digital baseband signal (S_(BB,1)) can vary depending on theparticular implementation. Further, any suitable digital splittingtechnique may be used. As one example, the digital signal splitter 26-1equally splits the digital baseband signal (S_(BB,1)) into the basebandsplit signals (S_(BB,1-1) through S_(BB,1-N)). As another example, ifthe multi-band MOPA 18 is a 2^(nd) order Doherty amplifier, the digitalsignal splitter 26-1 may provide the entire digital baseband signal(S_(BB,1)) to the baseband split signal (S_(BB,1-1)) when a voltage ofthe digitally represented signal is less than a predefined threshold andequally split the digital baseband signal (S_(BB,1)) across the basebandsplit signals (S_(BB,1-1) and S_(BB,1-2)) when the voltage of thedigitally represented signal is greater than or equal to the predefinedthreshold. As yet another example, if the multi-band MOPA 18 is a 2^(nd)order Doherty amplifier, the digital signal splitter 26-1 may providepeaks of the digital baseband signal (S_(BB,1)) to the baseband splitsignal (S_(BB,1-2)) and the remaining non-peak portion of the digitalbaseband signal (S_(BB,1)) to the baseband split signal (S_(BB,1-1)).The examples above are only examples and are not intended to limit thescope of the present disclosure.

The digital upconverters 28(1-1) through 28(1-N) digitally upconvert thebaseband split signals (S_(BB,1-1) through S_(BB,1-N)), respectively, toa desired upconversion frequency for the first frequency band, therebyproviding upconverted split signals (S_(UP,1-1) through S_(UP,1-N)). Inone embodiment, the desired upconversion frequency is a carrierfrequency for the first frequency band of the multi-band signal(S_(MB)). However, the desired upconversion frequency is not limitedthereto. The digital upconverters 28(1-1) through 28(1-N) each includeone or more calibration actuators that control a gain, phase, and delayof the corresponding upconverted split signal. Thus, the digitalupconverter 28(1-1) includes one or more calibration actuators thatcontrol a gain (G₁₋₁), phase (φ₁₋₁), and delay (τ₁₋₁) of the upconvertedsplit signal (S_(UP,1-1)). Likewise, the digital upconverter 28(1-N)includes one or more calibration actuators that control a gain(G_(1-N)), phase (φ_(1-N)), and delay (τ_(1-N)) of the upconverted splitsignal (S_(UP,1-N)).

In the same manner, the digital signal splitter 26-M operates to splitthe digital baseband signal (S_(BB,M)) into N baseband split signals(S_(BB,M-1) through S_(BB,M-N)) each corresponding to a different order,or input, of the multi-band MOPA 18. As discussed above with respect tothe digital signal splitter 26-1, the manner in which the digital signalsplitter 26-M splits the digital baseband signal (S_(BB,M)) can varydepending on the particular implementation. Further, any suitablesplitting technique may be used. The digital upconverters 28(M-1)through 28(M-N) digitally upconvert the baseband split signals(S_(BB,M-1) through S_(BB,M-N)), respectively, to a desired upconversionfrequency for the M-th frequency band, thereby providing upconvertedsplit signals (S_(UP,M-1) through S_(UP,M-N)). The digital upconverters28(M-1) through 28(M-N) each include one or more calibration actuatorsthat control a gain, phase, and delay of the corresponding upconvertedsplit signal. Thus, the digital upconverter 28(M-1) includes one or morecalibration actuators that control a gain (G_(M-1)), phase (φ_(M-1)),and delay (τ_(M-1)) of the upconverted split signal (S_(UP,M-1)).Likewise, the digital upconverter 28(M-N) includes one or morecalibration actuators that control a gain (G_(M-N)), phase (φ_(M-N)),and delay τ_(M-N)) of the upconverted split signal (S_(UP,M-N)).

Next, the digital combiners 30-1 through 30-N combine the upconvertedsplit signals for the corresponding orders, or inputs, of the multi-bandMOPA 18 to provide corresponding combined digital signals (S_(COMB-1)through S_(COMB-N)). Each of the combined digital signals (S_(COMB-1)through S_(COMB-N)) is a multi-band digital signal that includes theupconverted split signals for the respective order of the multi-bandMOPA 18. More specifically, the digital combiner 30-1 combines theupconverted split signals (S_(UP,1-1) through S_(UP,M-1)) for the firstorder, or first input 22-1, of the multi-band MOPA 18 to provide thecombined digital signal (S_(COMB-1)) for the first order of themulti-band MOPA 18. Likewise, the digital combiner 30-N combines theupconverted split signals (S_(UP,1-N) through S_(UP,M-N)) for the N-thorder, or N-th input 22-N, of the multi-band MOPA 18 to provide thecombined digital signal (S_(COMB-N)) for the N-th order of themulti-band MOPA 18. The D/A converters 32-1 through 32-N thendigital-to-analog convert the combined digital signals (S_(COMB-1)through S_(COMB-N)), respectively, to provide the multi-band analogsignals (S_(ANALOG-1) through S_(ANALOG-N)), which are also referred toherein as combined analog signals.

Lastly, the multi-band analog signals (S_(ANALOG-1) throughS_(ANALOG-N)) are processed by the analog circuitries 24-1 through 24-N,respectively, to provide the multi-band split signals (S_(MB-1) throughS_(MB-N)) to the respective inputs 22-1 through 22-N of the multi-bandMOPA 18. The analog circuitries 24-1 through 24-N may include anydesired analog circuitry such as, for example, one or more analogfilters that operate to remove undesired frequency components from themulti-band analog signals (S_(ANALOG-1) through S_(ANALOG-N)) and,potentially, one or more pre-amplifiers.

Importantly, the calibration actuators in the digital upconverters28(1-1) through 28(M-N) independently control the gains (G₁₋₁ throughG_(M-N)), phases (φ₁₋₁ through φ_(M-N)), and delays (τ₁₋₁ throughτ_(M-N)) of the upconverted split signals (S_(UP,1-1) throughS_(UP,M-N)). In doing so, the calibration actuators in the digitalupconverters 28(1-1) through 28(M-N) independently control the gains,phases, and delays for each of the M frequency bands for each of themulti-band split signals (S_(MB-1) through S_(MB-N)). Notably,independent control of the gains (G₁₋₁ through G_(M-N)), phases (φ₁₋₁through φ_(M-N)) , and delays (τ₁₋₁ through τ_(M-N)) of the upconvertedsplit signals (S_(UP,1-1) through S_(UP,M-N)) is beneficial in that,while the effects on gain, phase, and delay of the digital circuitry inthe digital upconversion system 20 are deterministic, the effects ongain, phase, and delay of the analog circuitries 24-1 through 24-N arenon-deterministic (e.g., variations over temperature, variations inmanufacturing, aging, etc.).

Preferably, using the calibration actuators in the digital upconverters28(1-1) through 28(M-N), the gains (G₁₋₁ through G_(M-N)), phases (φ₁₋₁through φ_(M-N)), and delays (τ₁₋₁ through τ_(M-N)) of the upconvertedsplit signals (S_(UP,1-1) through S_(UP, M-N)), and thus the gains,phases, and delays for each of the M frequency bands for each of themulti-band split signals (S_(MB-1) through S_(MB-N)), are independentlycontrolled, or configured, to optimize one or more performanceparameters (e.g., efficiency, linearity, and/or output power) of themulti-band MOPA 18. Note that, in another embodiment, the gains, phases,and delays for each of the M frequency bands for each of only N-1 of theupconverted split signals (S_(UP,1-1) through S_(UP,M-N)) may becalibrated since it may be preferable to control the offsets between thegains, phases, and delays, rather than their absolute values. In oneembodiment, the one or more performance parameters include efficiencyand one or both of linearity and output power. In one particularembodiment, using the calibration actuators in the digital upconverters28(1-1) through 28(M-N), the gains (G₁₋₁ through G_(M-N)), phases (φ₁₋₁through φ_(M-N)), and delays (τ₁₋₁ through τ_(M-N)) of the upconvertedsplit signals (S_(UP,1-1) through S_(UP,M-N)), and thus the gains,phases, and delays for each of the M frequency bands for each of themulti-band split signals (S_(MB-1) through S_(MB-N)), are independentlycontrolled, or configured, to maximize an efficiency of the multi-bandMOPA 18 while maintaining sufficient linearity to satisfy one or morepredefined requirements for the multi-band MOPA 18 (e.g., predefinedemissions requirements).

The values for the gains (G₁₋₁ through G_(M-N)), phases (φ₁₋₁ throughφ_(M-N)), and delays (τ₁₋₁ through τ_(M-N)) of the upconverted splitsignals (S_(UP,1-1) through S_(UP,M-N)) may be selected, or calibrated,using any suitable technique. In one particular embodiment, values forthe gains (G₁₋₁ through G_(M-N)), phases (φ₁₋₁ through φ_(M-N)), anddelays (τ₁₋₁ through τ_(M-N)) of the upconverted split signals(S_(UP,1-1) through S_(UP,M-N)) are selected in a factory calibrationprocess. For instance, one or more performance parameters of themulti-band MOPA 18 may be measured while adjusting the values for thegains (G₁₋₁ through G_(M-N)), phases (φ₁₋₁ through φ_(M-N)), and delays(τ₁₋₁ through τ_(M-N)) of the upconverted split signals (S_(UP,1-1)through S_(UP,M-N)) using any suitable algorithm until the values thatprovide the desired optimization of the one or more performanceparameters are determined. These values may then be stored by thedigital upconversion system 20 or otherwise programmed into the digitalupconversion system 20 and utilized during operation of the multi-bandMOPA 18. In another embodiment, the values for the gains (G₁₋₁ throughG_(M-N)), phases (φ₁₋₁ through φ_(M-N)), and delays (τ₁₋₁ throughτ_(M-N)) of the upconverted split signals (S_(UP,1-1) through S_(U,M-N))may be selected dynamically based on measurements of the multi-bandoutput signal (S_(OUT)) during operation of the multi-band MOPA 18. Inthis manner, the values for the gains (G₁₋₁ through G_(M-N)), phases(φ₁₋₁ through φ_(M-N)), and delays (τ₁₋₁ through τ_(M-N)) of theupconverted split signals (S_(UP,1-1) through S_(UP,M-N)) can be updatedover time as needed to optimize the one or more performance parametersof the multi-band MOPA 18.

FIG. 3 is a more detailed illustration of one of the digitalupconverters 28(1-1) through 28(M-N) of FIG. 2, which is generallydesignated as 28(X-Y), according to one embodiment of the presentdisclosure. As illustrated, the digital upconverter 28(X-Y) includes anumber of calibration actuators 34, a digital upconverter chain 36, and,in some embodiments, a Rate Change Filter (RCF) 38. The RCF 38 may bedesired if a sampling rate of the baseband split signal (S_(BB,X-Y)) isnot equal to f_(S)/N_(US), where f_(S) is an effective sampling rate ofthe D/A converter 32-Y and N_(US) is an up-sampling rate of an upsampler40 of the digital upconverter chain 36. In effect, the RCF 38 is abridge between the sampling rate of the baseband split signal(S_(BB,X-Y)) and the effective sampling rate of the D/A converter 32-Y.

As illustrated, in this embodiment, the baseband split signal(S_(BB,X-Y)) is a complex signal. In some embodiments, the sampling rateof the baseband split signal (S_(BB,X-Y)) is changed by the RCF 38.Then, the baseband split signal (S_(BB,X-Y)) is provided to thecalibration actuators 34. In general, the calibration actuators 34control the gain (G_(X-Y)), phase (φ_(X-Y)), and delay (τ_(X-Y)) of theupconverted split signal (S_(UP,X-Y)) via corresponding calibrationvalues (G_(X-Y,CAL), φ_(X-Y,CAL), and τ_(X-Y,CAL)). More specifically,the calibration actuators 34 include an equalizer 42, complexmultipliers 44 and 46, a coarse delay circuit 48, and a fine delaycircuit 50. Note that the ordering of the equalizer 42, the complexmultipliers 44 and 46, the coarse delay 48, and the fine delay 50 may bechanged. The equalizer 42 operates to effectively equalize the responseof the corresponding analog circuitry 24-Y. The complex multipliers 44and 46 multiply the equalized baseband split signal by the phase andgain calibration values (φ_(X-Y,CAL) and G_(X-Y,CAL)), respectively. Thephase and gain calibration values (φ_(X-Y,CAL) and G_(X-Y,CAL)) are suchthat the upconverted split signal (S_(UP,X-Y)) has the desired phase(φ_(X-Y)) and gain (G_(X-Y)). Notably, in one alternative embodiment,the complex multipliers 44 and 46 are combined into a single complexmultiplier that calibrates both gain and phase. Before proceeding, itshould be noted that while, in this embodiment, the calibrationactuators 34 are implemented at baseband, the present disclosure is notlimited thereto. One or more, and possibly all, of the calibrationactuators 34 may implemented during or after digital upconversion.

The phase and gain calibrated baseband split signal is then passedthrough the coarse and fine delay circuits 48 and 50 to provide acalibrated baseband split signal (S_(BB) _(_) _(CAL,X-Y)). A coarsedelay applied by the coarse delay circuit 48 is controlled by a coarsedelay calibration value (τ_(X-Y,COARSE)). As one example, the coarsedelay circuit 48 may be implemented as a series of flip-flops, and thecoarse delay calibration value (τ_(X-Y,COARSE)) selects the output ofone of the flip-flops as the output of the coarse delay circuit 48,which thereby controls the delay provided by the coarse delay circuit48. A fine delay applied by the fine delay circuit 50 is controlled by afine delay calibration value (τ_(X-Y,FINE)). As one example, the finedelay circuit 50 may be implemented as a filter, where the fine delaycalibration value (τ_(X-Y,FINE)) is one or more filter coefficients.Together, the coarse and fine calibration values (τ_(X-Y,COARSE) andτ_(X-Y,FINE)) form a delay calibration value (τ_(X-Y,CAL)).

The calibrated baseband split signal (S_(BB) _(_) _(CAL,X-Y)) is thendigitally upconverted by the digital upconverter chain 36 to provide theupconverted split signal (S_(UP,X-Y)) at the desired upconversionfrequency. In one embodiment, the desired upconversion frequency is thecarrier frequency for the corresponding frequency band of the multi-bandsignal (S_(MB)). However, in other embodiments, the desired upconversionfrequency is a predetermined frequency that is selected such that, afterprocessing of the upconverted split signal (S_(UP,X-Y)) by the D/Aconverter 32-Y and the analog circuitry 24-Y, the resulting signal is atthe desired carrier frequency for the corresponding frequency band ofthe multi-band signal (S_(MB)).

In this example, the digital upconverter chain 36 includes a complextuner 56 that tunes the calibrated baseband split signal (S_(BB) _(_)_(CAL,X-Y)), which is a complex signal, to a desired frequency. Thecomplex tuner 56 tunes the calibrated baseband split signal (S_(BB) _(_)_(CAL,X-Y)) to a desired baseband tuning frequency to thereby produce acomplex tuned digital split signal. In one embodiment, the basebandtuning frequency is programmable or otherwise selectable within a rangeof −f_(S)/2N_(US) and f_(S)/2N_(US), where f_(s) is the effectivesampling rate of the D/A converter 32-Y and N_(US) is the up-samplingrate of the upsampler 40.

The upsampler 40 up-samples the complex tuned digital split signal atthe up-sampling rate N_(US), where N_(US)≧2, to produce an upsampleddigital split signal having a sampling rate of f_(s). In the frequencydomain, the upsampled digital split signal includes N_(US) images of thecomplex tuned digital split signal equally spaced apart in the frequencyrange of 0 to f_(S), where f_(S) is the effective sampling rate of theD/A converter 32-Y. An image selection filter 54 filters the upsampleddigital split signal to select a desired one of the images of thecomplex tuned digital split signal and thereby provide a filtered splitsignal. More specifically, the image selection filter 54 is preferablyprogrammable via one or more parameters (e.g., filter coefficients) suchthat a passband of the image selection filter 54 is centered at adesired filter tuning frequency. The filter tuning frequency is selectedsuch that the desired image of the complex tuned digital split signalfalls within the passband of the image selection filter 54.

A digital quadrature modulator 56 performs quadrature modulation on thefiltered split signal to provide the upconverted split signal(S_(UP,X-Y)) output by the digital upconverter chain 36. In thefrequency domain, quadrature modulation results in frequencytranslating, or frequency-shifting, the image of the complex tuneddigital split signal in the filtered split signal by f_(QMOD), wheref_(QMOD) is a modulation frequency of the digital quadrature modulator56, and converting the complex signal into a real signal. The modulationfrequency (f_(QMOD)) can be any desired frequency including zero. Afterdigital quadrature modulation, the frequency-translated image of thecomplex tuned digital split signal is centered at the desiredupconversion frequency for the digital upconverter chain 36.

Notably, the digital quadrature modulator 56 may be configurable tooperate on a definition of quadrature modulation as a+jb or a−jb. Thismay be desirable because, for example, different cellular communicationstandards (e.g., Code Division Multiple Access (CDMA) 2000 and 3^(rd)Generation Partnership Project (3GPP)) may define quadrature modulationdifferently. Therefore, in order to accommodate different communicationstandards, the digital quadrature modulator 56 may be configurable inthis manner. Alternatively, this configuration may be handled by acomplex conjugate function prior to the complex tuner 52 that can beactivated or deactivated as needed. Further, in one embodiment, thedigital quadrature modulator 56 may be combined with the image selectionfilter 54.

For more information regarding the digital upconverter chain 36 and someexample implementations of the complex tuner 52, the upsampler 40, theimage selection filter 54, and the digital quadrature modulator 56, theinterested reader is directed to commonly owned and assigned U.S. PatentApplication Publication No. 2010/0098191 A1, entitled METHODS ANDSYSTEMS FOR PROGRAMMABLE DIGITAL UP-CONVERSION, filed on Oct. 20, 2008and published on Apr. 22, 2010, which is incorporated herein byreference in its entirety. For example, while the upsampler 40 and theimage selection filter 54 may be implemented as separate components,they are not limited thereto. The upsampler 40 and the image selectionfilter 54 may alternatively be implemented together as a polyphasefilter that performs both up-sampling and image selection filtering. Asanother example, the digital upconverter chain 36 may include multipleupsamplers 40 and image selection filters 54 arranged in a number ofupsampling and filtering stages. Also, while not essential to theunderstanding of the present disclosure, for further informationregarding digital upconversion, the interested reader is directed tocommonly owned and assigned U.S. patent application Ser. No. 13/490,801,entitled PROGRAMMABLE DIGITAL UP-CONVERSION FOR CONCURRENT MULTI-BANDSIGNALS, filed on Jun. 7, 2012, which is incorporated herein byreference in its entirety.

The digital upconversion system 20 including the independent control ofgain, phase, and delay of the upconverted split signals (S_(UP,1-1)through S_(UP,M-N)) enables precise control of the gain, phase, anddelay for each of the M frequency bands for each of the multi-band splitsignals (S_(MB-1) through S_(MB-N)). One benefit of this precise controlis that the gain, phase, and delay for each of the M frequency bands foreach of the multi-band split signals (S_(MB-1) through S_(MB-N)) can beconfigured such that the multi-band MOPA 18 operates at a desiredoperating point. This desired operating point may be selected tooptimize one or more performance parameters (e.g., efficiency,linearity, and/or output power).

The following acronyms are used throughout this disclosure.

3GPP 3^(rd) Generation Partnership Project

CDMA Code Division Multiple Access

D/A Digital-to-Analog

DAC Digital-to-Analog Converter

EER Envelope Elimination and Restoration

LINC Linear Amplification with Nonlinear Components

MOPA Multi-Order Power Amplifier

RF Radio Frequency

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A system comprising: a multi-band multi-orderpower amplifier configured to amplify a multi-band signal split across aplurality of inputs of the multi-band multi-order power amplifier as aplurality of multi-band split signals, the plurality of inputscomprising a different input for each of N orders of the multi-bandmulti-order power amplifier where N is greater than or equal to 2; and adigital upconversion system for the multi-band multi-order poweramplifier that is configured to control a gain, phase, and delay foreach of M frequency bands of the multi-band signal for each of at leastN-1 of the plurality of multi-band split signals independently from thegains, phases, and delays of other multi-band split signals.
 2. Thesystem of claim 1 wherein the digital upconversion system is configuredto independently control the gain, phase, and delay for each of the Mfrequency bands of the multi-band signal for each of the at least N-1 ofthe plurality of multi-band split signals such that one or moreperformance parameters of the multi-band multi-order power amplifier areoptimized.
 3. The system of claim 2 wherein the one or more performanceparameters comprise efficiency and at least one of a group consisting oflinearity and output power.
 4. The system of claim 1 wherein the digitalupconversion system is configured to independently control the gain,phase, and delay for each of the M frequency bands of the multi-bandsignal for each of the at least N-1 of the plurality of multi-band splitsignals such that an efficiency of the multi-band multi-order poweramplifier is maximized while maintaining sufficient linearity to satisfyone or more predefined requirements for the multi-band multi-order poweramplifier.
 5. The system of claim 1 wherein the multi-band signalcomprises M narrowband signals in the M frequency bands of themulti-band signal wherein M is greater than or equal to 2, and thedigital upconversion system comprises, for each frequency band of the Mfrequency bands of the multi-band signal: a digital signal splitter thatsplits a digital baseband signal for the frequency band into N basebandsplit signals for the frequency band, each of the N baseband splitsignals for the frequency band being for a different order of the Norders of the multi-band multi-order power amplifier; and for eachbaseband split signal for the frequency band of the N baseband splitsignals for the frequency band, a digital upconverter that upconvertsthe baseband split signal for the frequency band to a desiredupconversion frequency to thereby provide an upconverted split signalfor the frequency band, the digital upconverter comprising one or morecalibration actuators configured to control a gain, phase, and delay ofthe upconverted split signal for the frequency band.
 6. The system ofclaim 5 wherein the digital upconversion system further comprises, foreach order of the N orders of the multi-band multi-order poweramplifier: a digital combiner configured to digitally combine theupconverted split signals for the M frequency bands of the multi-bandsignal for the order of the multi-band multi-order power amplifier toprovide a combined upconverted digital signal for the order of themulti-band multi-order power amplifier; and a digital-to-analogconverter configured to digital-to-analog convert the combinedupconverted digital signal for the order of the multi-band multi-orderpower amplifier to provide a combined upconverted analog signal for theorder of the multi-band multi-order power amplifier.
 7. The system ofclaim 6 further comprising, for each order of the N orders of themulti-band multi-order power amplifier: analog circuitry configured toprocess the combined upconverted analog signal for the order of themulti-band multi-order power amplifier to provide one of the pluralityof multi-band split signals for one of the plurality of inputs of themulti-band multi-order power amplifier that corresponds to the order ofthe multi-band multi-order power amplifier.
 8. The system of claim 7wherein the one or more calibration actuators of each of the digitalupconverters for the N baseband split signals for each of the Mfrequency bands of the multi-band signal are configured to independentlycontrol a gain, phase, and delay for each of the M frequency bands ofthe multi-band signal for each of the plurality of multi-band splitsignals such that one or more performance parameters of the multi-bandmulti-order power amplifier are optimized.
 9. The system of claim 8wherein the one or more performance parameters comprise efficiency andat least one of a group consisting of linearity and output power. 10.The system of claim 7 wherein the one or more calibration actuators ofeach of the digital upconverters for the N baseband split signals foreach of the M frequency bands of the multi-band signal are configured toindependently control a gain, phase, and delay for each of the Mfrequency bands of the multi-band signal for each of the plurality ofmulti-band split signals such that an efficiency of the multi-bandmulti-order power amplifier is maximized while maintaining sufficientlinearity to satisfy one or more predefined requirements for themulti-band multi-order power amplifier.
 11. A digital upconversionsystem for a multi-band multi-order power amplifier configured toamplify a multi-band signal split across a plurality of inputs of themulti-band multi-order power amplifier as a plurality of multi-bandsplit signals, the plurality of inputs comprising a different input foreach of N orders of the multi-band multi-order power amplifier where Nis greater than or equal to 2 and the multi-band signal comprises Mnarrowband signals in M frequency bands of the multi-band signal whereinM is greater than or equal to 2, comprising: for each frequency band ofthe M frequency bands of the multi-band signal: a digital signalsplitter that splits a digital baseband signal for the frequency bandinto N baseband split signals for the frequency band, each of the Nbaseband split signals for the frequency band being for a differentorder of the N orders of the multi-band multi-order power amplifier; andfor each baseband split signal for the frequency band of the N basebandsplit signals for the frequency band, a digital upconverter thatupconverts the baseband split signal for the frequency band to a desiredupconversion frequency to thereby provide an upconverted split signalfor the frequency band, the digital upconverter comprising one or morecalibration actuators configured to control a gain, phase, and delay ofthe upconverted split signal for the frequency band; and circuitryconfigured to process the upconverted split signals for the M frequencybands of the multi-band signal for each of the N orders of themulti-band multi-order power amplifier to provide the plurality ofmulti-band split signals for the plurality of inputs of the multi-bandmulti-order power amplifier.
 12. The digital upconversion system ofclaim 11 wherein the digital upconversion system further comprises, foreach order of the N orders of the multi-band multi-order poweramplifier: a digital combiner configured to digitally combine theupconverted split signals for the M frequency bands of the multi-bandsignal for the order of the multi-band multi-order power amplifier toprovide a combined upconverted digital signal for the order of themulti-band multi-order power amplifier; and a digital-to-analogconverter configured to digital-to-analog convert the combinedupconverted digital signal for the order of the multi-band multi-orderpower amplifier to provide a combined upconverted analog signal for theorder of the multi-band multi-order power amplifier.
 13. The digitalupconversion system of claim 12 wherein, for each order of the N ordersof the multi-band multi-order power amplifier, the combined upconvertedanalog signal for the order of the multi-band multi-order poweramplifier is processed by analog circuitry to provide one of theplurality of multi-band split signals for one of the plurality of inputsof the multi-band multi-order power amplifier that corresponds to theorder of the multi-band multi-order power amplifier.
 14. The digitalupconversion system of claim 13 wherein the one or more calibrationactuators of each of the digital upconverters for the N baseband splitsignals for each of the M frequency bands of the multi-band signal areconfigured to independently control a gain, phase, and delay for each ofthe M frequency bands of the multi-band signal for each of the pluralityof multi-band split signals such that one or more performance parametersof the multi-band multi-order power amplifier are optimized.
 15. Thedigital upconversion system of claim 14 wherein the one or moreperformance parameters comprise efficiency and at least one of a groupconsisting of linearity and output power.
 16. The digital upconversionsystem of claim 13 wherein the one or more calibration actuators of eachof the digital upconverters for the N baseband split signals for each ofthe M frequency bands of the multi-band signal are configured toindependently control a gain, phase, and delay for each of the Mfrequency bands of the multi-band signal for each of the plurality ofmulti-band split signals such that an efficiency of the multi-bandmulti-order power amplifier is maximized while maintaining sufficientlinearity to satisfy one or more predefined requirements for themulti-band multi-order power amplifier.
 17. A method comprising:amplifying, via a multi-band multi-order power amplifier, a multi-bandsignal split across a plurality of inputs of the multi-band multi-orderpower amplifier as a plurality of multi-band split signals, theplurality of inputs comprising a different input for each of N orders ofthe multi-band multi-order power amplifier where N is greater than orequal to 2; and controlling a gain, phase, and delay for each of Mfrequency bands of the multi-band signal for each of at least N-1 of theplurality of multi-band split signals independently from the gains,phases, and delays of other multi-band split signals.
 18. The method ofclaim 17 wherein independently controlling the gain, phase, and delayfor each of the M frequency bands of the multi-band signal for each ofthe at least N-1 of the plurality of multi-band split signals comprises:independently and digitally controlling the gain, phase, and delay foreach of the M frequency bands of the multi-band signal for each of theat least N-1 of the plurality of multi-band split signals at baseband.19. The method of claim 17 wherein independently controlling the gain,phase, and delay for each of the M frequency bands of the multi-bandsignal for each of the at least N-1 of the plurality of multi-band splitsignals comprises: independently controlling the gain, phase, and delayfor each of the M frequency bands of the multi-band signal for each ofthe at least N-1 of the plurality of multi-band split signals such thatone or more performance parameters of the multi-band multi-order poweramplifier are optimized.
 20. The method of claim 19 wherein the one ormore performance parameters comprise efficiency and at least one of agroup consisting of linearity and output power.
 21. The method of claim17 wherein independently controlling the gain, phase, and delay for eachof the M frequency bands of the multi-band signal for each of the atleast N-1 of the plurality of multi-band split signals comprises:independently controlling the gain, phase, and delay for each of the Mfrequency bands of the multi-band signal for each of the at least N-1 ofthe plurality of multi-band split signals such that an efficiency of themulti-band multi-order power amplifier is maximized while maintainingsufficient linearity to satisfy one or more predefined requirements forthe multi-band multi-order power amplifier.
 22. The method of claim 17wherein the multi-band signal comprises M narrowband signals in the Mfrequency bands of the multi-band signal wherein M is greater than orequal to 2, and independently controlling the gain, phase, and delay foreach of the M frequency bands of the multi-band signal for eachmulti-band split signal of the plurality of multi-band split signalscomprises, for each frequency band of the M frequency bands of themulti-band signal: digitally splitting a digital baseband signal for thefrequency band into N baseband split signals for the frequency band,each of the N baseband split signals for the frequency band being for adifferent order of the N orders of the multi-band multi-order poweramplifier; and for each baseband split signal for the frequency band ofthe N baseband split signals for the frequency band, digitallyupconverting the baseband split signal for the frequency band to adesired upconversion frequency to thereby provide an upconverted splitsignal for the frequency band; wherein digitally upconverting thebaseband split signal for the frequency band comprises controlling again, phase, and delay of the upconverted split signal for the frequencyband.
 23. The method of claim 22 further comprising, for each order ofthe N orders of the multi-band multi-order power amplifier: digitallycombining the upconverted split signals for the M frequency bands of themulti-band signal for the order of the multi-band multi-order poweramplifier to provide a combined upconverted digital signal for the orderof the multi-band multi-order power amplifier; and digital-to-analogconverting the combined upconverted digital signal for the order of themulti-band multi-order power amplifier to provide a combined upconvertedanalog signal for the order of the multi-band multi-order poweramplifier.
 24. The method of claim 23 further comprising, for each orderof the N orders of the multi-band multi-order power amplifier:processing, via analog circuitry, the combined upconverted analog signalfor the order of the multi-band multi-order power amplifier to provideone of the plurality of multi-band split signals for one of theplurality of inputs of the multi-band multi-order power amplifier thatcorresponds to the order of the multi-band multi-order power amplifier.25. The method of claim 24 wherein controlling the gain, phase, anddelay of the upconverted split signal of each of the M frequency bandsof the multi-band signal for each of the N orders of the multi-bandmulti-order power amplifier is such that one or more performanceparameters of the multi-band multi-order power amplifier are optimized.26. The method of claim 25 wherein the one or more performanceparameters comprise efficiency and at least one of a group consisting oflinearity and output power.
 27. The method of claim 24 whereincontrolling the gain, phase, and delay of the upconverted split signalof each of the M frequency bands of the multi-band signal for each ofthe N orders of the multi-band multi-order power amplifier is such thatan efficiency of the multi-band multi-order power amplifier is maximizedwhile maintaining sufficient linearity to satisfy one or more predefinedrequirements for the multi-band multi-order power amplifier.